1. Field of the Invention
This invention relates to a keyboard device for a keyboard musical instrument, such as an electronic piano.
2. Prior Art
Conventionally, this kind of keyboard device has been proposed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 2001-175244. Further, an example of another conventional keyboard device for an electronic piano is shown in FIG. 6. In this keyboard device 40, a plurality of keys 3 have rear ends pivotally supported by key fulcrums 5 provided on a chassis 2. The keys 3 are formed by synthetic resin molded articles and comprised of white keys 3a (only one of which is shown) and black keys 3b (only one of which is shown). The keys 3 each have a top wall 3c, and left and right side walls 3d, 3d (only one of which is shown), and a front wall 3e. The keys 3 are open downward. Further, each key 3 has L-shaped engaging portions 3f, 3f (only one of which is shown) extending downward from the respective left and right side walls 3d, 3d. Disposed between the rear end of the key 3 and the chassis 2 is a spring 12 for biasing the key 3 in the key-releasing direction (in the clockwise direction, as viewed in FIG. 6).
On the chassis 2, under respective front ends of the keys 3, there are mounted upper limit stoppers 6a and lower limit stoppers 6b, each formed e.g. by felt. The upper limit stoppers 6a are attached to a lower surface of the chassis 2, while the lower limit stoppers 6b are attached to an upper surface of the chassis 2. Hammers 4 are pivotally supported by a support shaft 4a on the chassis 2. An actuator portion 3g of the key 3 is in abutment with a portion of an associated one of the hammers 4 forward of the support shaft 4a, from above. Further, the chassis 2 has a large number of key switches 7 (only one of which is shown) provided under the hammer 4, for detecting information of depression of each key 3.
Due to the construction described above, in the keyboard device 40, when any of the keys 3 is depressed from a key-off state shown in FIG. 6, the key 3 is pivotally moved downward about the associated key fulcrum 5. Then, when the lower surface of the key 3 is brought into abutment with the associated lower limit stopper 6b, the pivotal motion of the key 3 is stopped by the stopper 6b while alleviating the impact of collision of the key 3. The hammer 4 is pivotally moved in the anticlockwise direction as viewed in FIG. 6 by being urged via the actuator portion 3g of the key 3. In accordance with the pivotal motion of the hammer 4, the key switch 7 associated with the key 3 is pressed by the hammer 4 whereby depression of the key 3 and a speed of the depression are detected by the key switch 7. Generation of a tone is controlled based on the result of the detection. On the other hand, when released, the key 3 is pivotally moved upward about the key fulcrum 5 by the urging force of the spring 12 to thereby bring the engaging portions 3f, 3f into abutment with the associated upper limit stopper 6a. Thus, the key 3 is returned to the key-off state.
However, the conventional keyboard device 40 described above suffers from the following problems: In the keyboard device 40, since the keys 3 are open downward, when the depressed key 3 is brought into abutment with the lower limit stopper 6b, lower ends of the left and right side walls 3d, 3d are abutted against the lower limit stopper 6b, and hence the key 3 has very small abutment areas via which it is abutted against the stopper 6b. This means that the lower ends of the left and right side walls 3d, 3d press downward the lower limit stopper 6b, formed by felt, with load concentrated on the very small abutment areas. Therefore, as shown in FIG. 7, the lower ends of the left and right side walls 3d, 3d bite the lower limit stopper 6b to thereby largely deform the abutment portion in a manner sinking the same. The pivotal motion of the key 3 is not terminated immediately after the abutment, and continues during a certain time period until the deformation of the lower limit stopper 6b reaches a limit. As a result, when the key 3 is depressed, it is difficult to obtain a feeling (stop feeling) that the key 3 is stopped at a predetermined position. This adversely affects the key touch feeling.
Further, as described above, since the amount of deformation of the lower limit stopper 6b is large, plastic deformation is liable to occur, and it is difficult to restore the deformed stopper 6b to its original shape even after the pressed stopper 6b is released. This results in degraded durability of the lower limit stopper 6b, for example, causing deviation of abutting timing in which the key 3 is brought into abutment with the associated stopper 6b. 